The present invention relates to apparatus for ore deposit prospecting, and more particularly to devices for geophysical prospecting, or exploration by the polarization curve method of ore deposits featuring an electronic conductivity.
Known at present is a device for geophysical prospecting of ore deposits by the polarization curve method, effecting galvanodynamic excitation of electrochemical reactions (cf. U.S. Pat. No. 3.659.192 issued Apr. 25, 1972).
The graphical relationship between the intensity of the current I flowing through the surface of an ore body and the value of the potential .phi. of the electrochemical reaction excited by the flow of said current is referred to as "the polarization curve".
If the recording of polarization curves is accompanied by variations of the current flowing through the surface of an ore body according to a preset program, the process is referred to as the galvanodynamic method of investigating an ore body (the realtionship .phi. = f(I) ), see for example U.S. Pat. No. 3,758,846, issued Sept. 11, 1973. If the recording of polarization curves is carried out with the potential .phi. of electrochemical reactions on the surface of the ore body being set according to a program, one speaks of the potentiodynamic method of investigating an ore body (the relationship I = f(.phi.) ).
The above-mentioned device for geophysical prospecting of ore depositis comprises a direct-current source with a means for changing current intensity, a main current-carrying electrode having electrical contact with an ore body and connected to the direct-current source, and an auxiliary current-carrying electrode having electrical contact with the medium enclosing the ore body and connected to the direct-current source. Connected between the direct-current source and one of the current-carrying electrodes, for example, the main electrode, is a current intensity detector. The device also comprises a unit for measuring the potentials of electrochemical reactions on the surface of the ore body. Inputs of the unit are connected to a summing unit and the main current-carrying electrode. The inputs of the summing unit are connected to a non-polarizing measuring electrode and to a compensating voltage generator connected to the current intensity detector. Connected to the current intensity detector and the potential measuring unit is a unit for recording polarization curves, whereas a unit for setting the time of excitation by direct current of the ore body is connected to the means for changing current intensity.
Variations of the intensity of the current flowing through the circuit including the direct-current source, the ore body and the current-carrying electrodes, effected according to a preset program by the unit for setting the time of excitation by direct current of the ore body, excite successive electrochemical reactions on the surface of said ore body. Joint operation of the current intensity detector, the compensating voltage generator, the summing unit and the potential measuring unit results in discriminating the values of the electrochemical reaction potentials at the output of the latter unit, which are recorded by the recording unit in the form of relationships (.phi.=f (I) ).
The polarization curves, which are multistep curves, are used to determine the electrochemical reaction potentials which, in turn, are used to determine the mineral composition of ore bodies and the values of the limiting current intensity of the reactions which help to establish the dimensions of ore bodies and other parameters thereof.
Yet, the galvanodynamic method of exciting electrochemical reactions, effected by the known device, has a disadvantage if there are excited electrochemical reactions having reaction potentials close to one another, it is difficult to distinguish these on a polarization curve. In addition, there often occurs a smooth transition from recording the potential of one electrochemical reaction to recording the potential of another electrochemical reaction (for example, in the case of streak-impregnation ores), which may lead to difficulties in determining the electrochemical reaction potentials on the polarization curve and, in particular, of the values of the limiting current intensity of these reactions and, consequently, to errors in determining the mineral composition of ores, especially with regard to small concentrations of minerals, as well as errors in determining the amount of minerals and the dimensions of ore bodies.